No abstract available.
Polymers*

No abstract available.
Polymers*

The study was carried out on 48 workers producing polymer-composite material for over 2 years. The results showed that: although the exposure time is not so long, the polymer-composite material producing has influenced badly to workers' health such as: headache, fatigue... Workers have to be off more because of illness. There are functional changes of central nervous system such as: longer simple reaction time, impairment of short-term memory; decrease of concentration; decrease of electrical activeness of cerebral cortex and sleepy disorder.
Health ; Polymers

This study aimed to determine whether the curing times of Xtra Power and High Power modes of high-power light emitting diode (LED) curing light are sufficient for polymerization of resin sealants. The specimens were prepared and their microhardness values were measured and compared with those of specimens polymerized under conventional LED curing light.The filled sealant polymerized for 8 seconds in the High Power mode and for 3 seconds in the Xtra Power mode showed significantly lower microhardness than the control specimen (p = 0.000). The unfilled sealant polymerized for 8, 12 seconds in the High Power mode and for 6 seconds in the Xtra Power mode showed significantly lower microhardness than the control specimen (p = 0.000).The results of this study suggest that the short curing time with the Xtra Power and High Power modes of highpower LED curing light are not sufficient for adequate polymerization of sealants under specific conditions, taking into account the curing times and the type of sealant.
Polymerization ; Polymers

PURPOSE: Polymer infiltrated ceramic network (PICN) materials, also called hybrid ceramics, are new materials in dental market. The manufacturer of the PICN material VITA Enamic suggests 3 different finishing procedures for this new material. In the present study, surface roughness and color differences caused from different finishing procedures of VITA Enamic were investigated. MATERIALS AND METHODS: 120 specimens were prepared in dimensions 2 x 10 x 12 mm from VITA Enamic hybrid ceramic blocks with 'high translucency' and 'translucency 2M2' shades. The specimens were divided into 8 groups. For each group, different finishing procedures suggested by the manufacturer were performed. Surface roughness values were determined by a tactile portable profilometer. Color changes were evaluated using a clinical spectrophotometer. The data were analyzed using one-way ANOVA and Tukey's post-hoc comparison. The significance level was set at alpha=0.05. RESULTS: The roughest surfaces were observed in Glaze Groups. Their surface roughness values were similar to that of the control group. Clinical Kit and Technical Kit groups did not show a statistically significant difference regarding surface roughness (P>.05). The largest color difference regarding DeltaE00 was observed in Clinical Kit finishing groups. There were also statistically significant color changes between the groups (P<.05). However, all the groups showed clinically acceptable color change (DeltaE(00)<2.25) except Clinical Kit Groups (DeltaE(00)>2.25). CONCLUSION: Within the limitations of the present study, it may be suggested that finishing the VITA Enamic restorations by Technical Kit instead of Glaze and Clinical Kit gives better clinical performance in regard to surface roughness and shade matching.
Ceramics* ; Polymers*

No abstract available.
Genetic Therapy* ; Polymers*

PURPOSE: This study was designed to compare the amount of polymerization shrinkage of dual-cure resin cements according to different polymerization modes and to determine the effect of light activation on the degree of polymerization. MATERIALS AND METHODS: Four kinds of dual-cure resin cements were investigated: Smartcem 2, Panavia F 2.0, Clearfil SA Luting and Zirconite. Each material was tested in three different polymerization modes: self-polymerization only, immediate light polymerization and 5 minutes-delayed light polymerization. The time-dependent polymerization shrinkage-strain was evaluated for 30 minutes by Bonded-disk method at 37degrees C. Five recordings of each material with three different modes were taken. Data were analyzed using one-way ANOVA and multiple comparison Scheffe'test (alpha=.05). RESULTS: All materials, except Panavia F 2.0, exhibited the highest polymerization shrinkage-strain through delayed light-activated polymerization. No significant difference between light activation modes was found with Panavia F 2.0. All materials exhibited more than 90% of polymerization rate in the immediate or delayed light activated group within 10 minutes. CONCLUSION: As a clinical implication of this study, the application of delayed light activation mode to dual-cure resin cements is advantageous in terms of degree of polymerization.
Polymerization* ; Polymers* ; Resin Cements*

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.
Composite Resins* ; Polymerization ; Polymers

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.
Composite Resins* ; Polymerization ; Polymers

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior, these two factors should be considered. In this experiment, I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods. The composites used in this study can be categorized in two groups, one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme, Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress (sigmatheta) was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups. Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components, Filtek Supreme groups showed higher residual stress.
Composite Resins ; Polymerization ; Polymers